Aftermarket LTX blocks?

[Bullitt]

Ive been doing some digging around and Ive come to learn that the LTx aftermarket isnt that great, or I just dont know where to look... Ive heard rumor that there is a fabled LT block with 350 mains, a 4.120 unfinished bore, and is tall decked for a stroker kit... From what Ive read, Dart had this project in late 2008 and early 2009 but scrapped it due to tooling costs and lack of demand. I later found that GMPP had 13 or so of these blocks PRODUCED that float around on e-bay for $3-5K for JUST A BARE BLOCK, and thats where the trail goes cold... I ultimately want a 427 stroker LT4 of sorts, and Im not that willing to switch to an LSx platform just yet... can anyone give me a kick in the right direction?

[94Blackbird]

you'll have to get an aftermarket sbc block and modify it to work. There was an article in GMHTP awhile back about a guy who did a 414 cube all aluminum LTx in an Impala, but he started with a Dart block and had it extensively modified. The LTx aftermarket isn't that great because there are relitively few of us wanting performance parts for these motors. We are helped by the fact that a lot of Gen I SBC stuff can be made to work (I'm in the process of building a low comp LT1 with basically all factory 350 parts), but also hindered by just how different our motors are from anything else GM made.

If you want a 427 stroker, you're best bet is to get an aftermarket SBC block and have all the machine work performed to make it work with LTX heads and the reverse flow cooling system. Good luck finding one of the GMPP blocks, you are right, those things are RARE, and once in a blue moon comes around more often than one of those goes up for sale.

Dart did announce an aftermarket LTX block, but there was too little demand for the piece, so they tanked it until further notice.


LTX's are basically the redheaded step children of the SBC world. No one is quite sure what to do with us lol

[Bullitt]

Hmmm so it sounds like its going to be rather cost ineffective to go up to the 427. The entire reason I wanted one was because I could say, "yeah, its "just" an LT1" and scare the bejeezus out of a few supras Ive seen tooling around. Im not too keen on allowing someone to hack into an aftermarket Gen 1 block and have all kinds of holes all over the place either. Well it looks like Ill be going to the LS3 427 stroker kit, is the wiring x over difficult?

[mustangtraitor]

sighs.... the lt1 block is just a 350, get what u want its not a lt1 till u add heads, timing cover, intake and such

[joelster]

You can take a stock LT1 block out to 414". That is the limit as far as I know. It requires a few special parts to get it to fit, and a good machine shop, but it can be done. There may be more than 13 of those fabled bowtie bocks out there. 13 is the highest serial number that I have seen though. Brady aka "roadtrip120" has one sitting at his house. Dart claims there wasn't enough interest to justify producing them. Go to dartheads.com and click on their forums and take a look at the 2 LTx block threads. Those 2 threads were BY FAR their highest ever traffic recorded on their website. It was just bad timing. Right when they were going to go ahead with the build, the economy tanked.

[Fastbird]

Just an fyi, but the Impala guy in GMHTP was using an aluminum block and it was a 434 cid. Pretty trick setup but I don't want to know what he's got invested in it.

Postin' on the go......

[BadBlackZee]

The aftermarket blocks would be a nice option, but to be honest...the LT1 block has gone into some high horsepower numbers. I understand that you want to be different, but you can still put a hurting on anything out there with some work to the stock style platform. I just finished putting together my 383 that you see in my sig and its basically bulletproof, can take a hefty shot of nitrous, and claim almost anything out on the street.

Something to look into is running a modified SBC head for the LT1. Plenty of folks make some good numbers on solid roller setups with this option. Just food for thought...

[95ImpySS]

Last time I saw one of the blocks for sale it was on racingjunk.com I have to agree with badblackzee. If you build the bottom end and reenforce the block in key places. I don't see why a LT1 cant put out 2000 hp with quality components. Just no one has put the time and money into it. Would like to see what NelsonRacingEngines could produce with an avid LT1 Enthusiastist's money.

[Bullitt]

sighs.... the lt1 block is just a 350, get what u want its not a lt1 till u add heads, timing cover, intake and such
No offense, if it were "just a 350" there wouldnt be such a difficult time finding parts because vortec and gen I heads and the like are plentiful. If that were case there is a HUGE misconception with LTx owners everywhere that there isnt a low aftermarket following.


Just an fyi, but the Impala guy in GMHTP was using an aluminum block and it was a 434 cid. Pretty trick setup but I don't want to know what he's got invested in it.
LOL the 434 is what I HAD in my SS monte for a race motor. and you are right, for a good block and bottom end the are expensive.... I was in 5 figures for JUST the block and bottom end. Not wanting to go down that road again...

Postin' on the go......


You can take a stock LT1 block out to 414". That is the limit as far as I know. It requires a few special parts to get it to fit, and a good machine shop, but it can be done. There may be more than 13 of those fabled bowtie bocks out there. 13 is the highest serial number that I have seen though. Brady aka "roadtrip120" has one sitting at his house. Dart claims there wasn't enough interest to justify producing them. Go to dartheads.com and click on their forums and take a look at the 2 LTx block threads. Those 2 threads were BY FAR their highest ever traffic recorded on their website. It was just bad timing. Right when they were going to go ahead with the build, the economy tanked.
Isnt the 414 dangerously close to the water jackets? I think I was reading somewhere that it was REALLY bad at overheating and had problems with warping too. This is partially why I was looking so hard for that particular block, It would still have street manners that I could tool around, but have the torque to get down and dirty when the time called... Living in Miami is a LOT of stop and go traffic, hence my issue with the 414 for fear of overheating.

[dsmawd350]

2000hp on a stock lt1 block...idk about all that lol

[95ImpySS]

2000hp on a stock lt1 block...idk about all that lol

Wishful thinking :D hahaha

[joelster]

Isnt the 414 dangerously close to the water jackets? I think I was reading somewhere that it was REALLY bad at overheating and had problems with warping too. This is partially why I was looking so hard for that particular block, It would still have street manners that I could tool around, but have the torque to get down and dirty when the time called... Living in Miami is a LOT of stop and go traffic, hence my issue with the 414 for fear of overheating.

My block is NOT clearanced any more than a regular 383. It's in no danger of going into the water jackets, the block is not half-filled or anything like that either. The key is with the rods that are used. They are smaller on the cap end than a typical H-beam rod. That's why the block doesn't need to be opened up any more. They are Scat Pro-comp I beams. The shop did a little grinding on them, but nothing major. I run a small base circle cam (.900") but a mild .950" will fit too. My car runs about 20-30 degrees cooler right now than it did with the stock shortblock motor that was in the car before.

[BLK95-Z]

My block is NOT clearanced any more than a regular 383. It's in no danger of going into the water jackets, the block is not half-filled or anything like that either. The key is with the rods that are used. They are smaller on the cap end than a typical H-beam rod. That's why the block doesn't need to be opened up any more. They are Scat Pro-comp I beams. The shop did a little grinding on them, but nothing major. I run a small base circle cam (.900") but a mild .950" will fit too. My car runs about 20-30 degrees cooler right now than it did with the stock shortblock motor that was in the car before.

Whats the stroke on the crank your using? How did you get that much ci?

[joelster]

4.060" bore with a 4.00" stroke

[Bullitt]

Joelster, you mind if I ask how extensive (cost) the work was in the bottom end to have it all balanced, honed, etc? And also, Im assuming your setup is track only right? What I am looking for is dual purpose. only reason why I make that assumption is because of the size of your stall in your sig...

I guess Im asking for too much to be able to find a nice 4.120 unfinished bore block thats tall decked for a stroker and can squeeze a 4" stroke crank in it all while having 350 mains and be predrilled to accept LT parts... :(


Anyhow, heres my set up at the moment:
355 LT1, running a LT4 HOT cam with 1.6 roller rockers, Edelbrock heads and intake running a 58mm BBK throttlebody. Ive got the K&N cold air, Granatelli MAF sensor running Edelbrock headers and a 3" y to a single flowmaster. Its got the M6 (borg warner,,, not that tremec garbage) with a stage 2 clutch and a short shift with 3.42 eaton gears. I have the LT4 knock module, VATS delete, TB coolant bypass, MSD coil, and opti, and I KNOW I need a tune, and Ive been thinking about just buying the Jet DSA. aside from a few odds and ends and needing a suspension upgrade (PO rigged the car horridly) I think Im at the point where to get MORE power I'd need to spray the motor, but with 170k on the ticker, Im not comfortable dropping a 150 shot on it.... especially considering I dont know who did a lot of the work, or if the bottom end has any work done to it. Hence the reason I want a new block...

[joelster]

Joelster, you mind if I ask how extensive (cost) the work was in the bottom end to have it all balanced, honed, etc? And also, Im assuming your setup is track only right? What I am looking for is dual purpose. only reason why I make that assumption is because of the size of your stall in your sig...
I bought it fully built from a guy on LS1tech for $2169, lol, with a bunch of extra stuff thrown in for free. Yes I got a smoking deal. The block has typical machining for a stroker application which runs around $800-$1000. Boring, honing, aligning the mains, decking, drilling for 4-bolt main caps, etc, etc. That stuff is normal and your local shop can get you a price. The pistons are Mahle and run around $750 in Summit Racing, the crank is an Eagle forged crank which is around $750-$800 at Summit, and the rods are Scat Pro-comps which are $375ish at Summit. They took quite a bit of metal off of the crank to get it to balance. The pistons are very light and the I-beams are lighter than an H-beam. If I had to guess i'd say it was around $300-$400 for the balancing. The guy I bought it from probably had $4500 minimum tied up into the shortblock. A fully forged 383 will run you at least $3500 (if you find a smoking deal) and more than likely will be over $4000 as well.

My cars driveability is actually pretty good. The stall is mid-level and it is tight. It acts like a stock converter until you mash the gas. The cam I run is fairly big and could use more converter. I could easily throw in a hydraulic cam in the mid 240's and cruise this thing daily. I'm not sure how good it would be on gas though.


I guess Im asking for too much to be able to find a nice 4.120 unfinished bore block thats tall decked for a stroker and can squeeze a 4" stroke crank in it all while having 350 mains and be predrilled to accept LT parts... :(
You'd have to come up with some funky cooling lines to get an sbc block to be reverse cooled. There are GM Raceshop blocks out there still but be expected to pay $4000 when they pop up, and they will still need to be machined.



Anyhow, heres my set up at the moment:
355 LT1, running a LT4 HOT cam with 1.6 roller rockers, Edelbrock heads and intake running a 58mm BBK throttlebody. Ive got the K&N cold air, Granatelli MAF sensor running Edelbrock headers and a 3" y to a single flowmaster. Its got the M6 (borg warner,,, not that tremec garbage) with a stage 2 clutch and a short shift with 3.42 eaton gears. I have the LT4 knock module, VATS delete, TB coolant bypass, MSD coil, and opti, and I KNOW I need a tune, and Ive been thinking about just buying the Jet DSA. aside from a few odds and ends and needing a suspension upgrade (PO rigged the car horridly) I think Im at the point where to get MORE power I'd need to spray the motor, but with 170k on the ticker, Im not comfortable dropping a 150 shot on it.... especially considering I dont know who did a lot of the work, or if the bottom end has any work done to it. Hence the reason I want a new block...
If the oil pressure is good I would have no problem running nitrous through it. Especially since you won't be taking it to real high rpm's with the hotcam.

[Bullitt]

The oil pressure on the idiot gauge is around 20 to 25 psi at idle (1000 rpm) and will quickly rise to close to if not above 40 psi on acceleration. I have a sneaky feeling that a head gasket is getting ready to blow though. It is starting to lose compression and a little bit of coolant and has a small stumble. So a rebuild is going to be in order fairly soon. I agree with you on the 383 block, but I guess that Im just looking for a deal that isnt to be had :/. Your set up sounds killer and you got a hell of a deal on that motor!!!

[joelster]

Check the classified sections on the boards. With the economy the way it is, it isn't uncommon for brand new shortblocks to pop up for sale for a song every now and then.